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package com.oracle.truffle.regex.tregex.automaton;

import com.oracle.truffle.regex.tregex.util.json.JsonConvertible;

import java.util.Collection;

/**
 * Represents a set of NFA transitions to be used in {@link TransitionBuilder}.
 *
 * The set of NFA transitions implicitly also represents a set of NFA <em>target states</em>, which
 * should be used to determine equality between instances of this class.
 */
public interface TransitionSet extends JsonConvertible {

    /**
     * Create a merged set of {@code this} and {@code other} by copying {@code this} and adding the
     * contents of {@code other} to the copy.
     * 
     * @param other the {@link TransitionSet} to be merged with the copy. Implementing classes may
     *            accept objects of their own type only.
     * @return the merged set. <strong>MUST</strong> be of the same type as {@code this}!
     */
    TransitionSet createMerged(TransitionSet other);

    /**
     * Add the contents of {@code other} to {@code this}, analogous to
     * {@link java.util.Set#addAll(Collection)}.
     * 
     * @param other the {@link TransitionSet} to be merged with {@code this}. Implementing classes
     *            may accept objects of their own type only.
     */
    void addAll(TransitionSet other);

    /**
     * Returns the hash code value for this object.
     *
     * The hash should be calculated from the <strong>set of target states</strong> represented by
     * this transition set!
     */
    @Override
    int hashCode();

    /**
     * Checks if this transition set is equal to another.
     *
     * Two transition sets should be treated as equal if and only if their <strong>set of target
     * states</strong> is equal!
     */
    @Override
    boolean equals(Object obj);
}
